pascal dot haskell

pascal.hs

import Data.Semigroup
import Control.Comonad
import Control.Comonad.Store

pascalLine :: Store (Int, Int) Int -> Int
pascalLine w | x <= 0 = 1
             | y <= 0 = 1
             | otherwise = peek (x-1, y) w + peek (x, y-1) w
  where
    (x, y) = pos w

instance Semigroup Int where
  (<>) = (+)

pascal :: Store (Int, Int) Int
pascal = cfix pascalLine

test :: Int
test = peek (0,0) pascal -- infinitely loops